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Potential timing fix for read and write. #28

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merged 1 commit into from
May 23, 2013
+23 −11
Merged

Potential timing fix for read and write. #28

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34 changes: 23 additions & 11 deletions src/impl/unix.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -389,7 +389,8 @@ Serial::SerialImpl::available ()
}
}

inline void get_time_now(struct timespec &time)
inline void
get_time_now (struct timespec &time)
{
# ifdef __MACH__ // OS X does not have clock_gettime, use clock_get_time
clock_serv_t cclock;
Expand All @@ -404,6 +405,19 @@ inline void get_time_now(struct timespec &time)
# endif
}

inline void
diff_timespec (timespec &start, timespec &end, timespec &result) {
if (start.tv_sec > end.tv_sec) {
throw SerialExecption ("Timetravel, start time later than end time.");
}
result.tv_sec = end.tv_sec - start.tv_sec;
result.tv_nsec = end.tv_nsec - start.tv_nsec;
if (result.tv_nsec < 0) {
result.tv_nsec = 1e9 - result.tv_nsec;
result.tv_sec -= 1;
}
}

size_t
Serial::SerialImpl::read (uint8_t *buf, size_t size)
{
Expand Down Expand Up @@ -452,19 +466,18 @@ Serial::SerialImpl::read (uint8_t *buf, size_t size)
// Calculate difference and update the structure
get_time_now (end);
// Calculate the time select took
struct timeval diff;
diff.tv_sec = end.tv_sec - start.tv_sec;
diff.tv_usec = static_cast<int> ((end.tv_nsec - start.tv_nsec) / 1000);
struct timespec diff;
diff_timespec (start, end, diff);
// Update the timeout
if (total_timeout.tv_sec <= diff.tv_sec) {
total_timeout.tv_sec = 0;
} else {
total_timeout.tv_sec -= diff.tv_sec;
}
if (total_timeout.tv_usec <= diff.tv_usec) {
if (total_timeout.tv_usec <= (diff.tv_nsec / 1000)) {
total_timeout.tv_usec = 0;
} else {
total_timeout.tv_usec -= diff.tv_usec;
total_timeout.tv_usec -= (diff.tv_nsec / 1000);
}

// Figure out what happened by looking at select's response 'r'
Expand Down Expand Up @@ -552,19 +565,18 @@ Serial::SerialImpl::write (const uint8_t *data, size_t length)
// Calculate difference and update the structure
get_time_now(end);
// Calculate the time select took
struct timeval diff;
diff.tv_sec = end.tv_sec - start.tv_sec;
diff.tv_usec = static_cast<int> ((end.tv_nsec - start.tv_nsec) / 1000);
struct timespec diff;
diff_timespec(start, end, diff);
// Update the timeout
if (timeout.tv_sec <= diff.tv_sec) {
timeout.tv_sec = 0;
} else {
timeout.tv_sec -= diff.tv_sec;
}
if (timeout.tv_usec <= diff.tv_usec) {
if (timeout.tv_usec <= (diff.tv_nsec / 1000)) {
timeout.tv_usec = 0;
} else {
timeout.tv_usec -= diff.tv_usec;
timeout.tv_usec -= (diff.tv_nsec / 1000);
}
#endif

Expand Down